(a) Technical Field
The present invention relates to an anti-oxidant for rubber and synthetic rubber including the same, wherein the anti-oxidant contains a highly heat-resistant and environment-friendly thio compound.
(b) Background Art
In general, the conventional anti-oxidants of polymers can be classified into phenol-based, amine-based, phosphite-based, and thioester-based anti-oxidants. These anti-oxidants may be used alone or in any combination thereof. However, each of the anti-oxidants has its own limitation. Specifically, the phenol-based anti-oxidant shows a high thermostability at the initial stage, but is frequently colored after oxidation. Thus, its use has been largely limited. The amine-based anti-oxidant is excellent as an anti-oxidant, but has a problem in its color. The phosphite-based anti-oxidant has a disadvantage that it is hydrolyzed by water, and is decomposed in a stripping process during rubber synthesis. The thioester-based anti-oxidant normally cannot exhibit its performance when used alone but can only when used in combination with a primary anti-oxidant.
2,6-di-t-butyl-4-methylphenol (hereinafter, referred to as “BHT”) generally used in a polymer is a primary anti-oxidant, and is excellent in thermostability. However, it is volatile due to low molecular weight thus lowering its function as a heat-resistant additive while causing serious discoloration. Especially, the BHT may damage the liver, and cause allergies and tumors.
Since the BHT generally used in polymers can cause environmental pollution due to its volatility, BHT-free products have been required in industry. Accordingly, there is an urgent need for the development of an anti-oxidant that can prevent oxidation of polymers and maintain the intrinsic properties of the polymers, while not being harmful to human body and having low volatility.
At present, as BHT replacement materials, 1076(octadecyl-3-(3,5-di-t-butyl-4-hyroxyphenyl)-propionate), 1010 (pentaerythrityl-tetrakis[3-(3,5-di-t-butyl-4-hyroxyphenyl)-propionate]), etc., are used. However, they are merely primary anti-oxidants, and have limitations in their performance and physical properties thus requiring addition of a secondary anti-oxidant.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.